Draft Programmatic Environmental Impact Statement/Environmental Impact Report
San Francisco Estuary Invasive Spartina Project: Spartina Control Program
April 2003

Table 3.1-1:  Summary of Potential Hydrologic and Geomorphic Effects

 

Impact

Manual Removal
(Hand pulling and manual
excavation)

Mechanical
Removal
(Excavation, dredging, and shredding)

Pruning, Hand-mowing, and Smothering

Flooding
(Diking, drowning, and salinity
variation)

Burning

Herbicide
Application

Beneficial Effects

GEO-1: Erosion or deposition of sediment at sites of cordgrass
eradication.

All Alternatives:
Minor erosion and sedimentation.

 

All Alternatives:
Potentially
significant erosion.

 

All Alternatives:  Minor erosion
potential.

 

All Alternatives:
Potentially
significant erosion from diking
activities.

All Alternatives:  Minimal erosion potential.

 

All Alternatives:
Minor erosion
potential.

 

Alternatives 1, 2: Beneficial effect on sediment transport in tidal creeks, mudflats, marshes, and channels.

 

GEO-2: Erosion or topographic change of marsh and mudflat by vehicles used in eradication.

All Alternatives:
Minor impact from access.

 

All Alternatives:
Potentially
significant
microtopographic changes and
erosion from use
of vehicles in marshes.

 

All Alternatives:
Minor impact from access.

 

All Alternatives:
Potentially
significant
topographic changes from
diking activities.

 

All Alternatives:
Minor impact from access.

 

All Alternatives:
 Minor impact from access.

 

N/A

GEO-3: Remobilization of sand in cordgrass-stabilized
estuarine beaches.

All Alternatives:
Minor increased beach erosion and sedimentation.

 

All Alternatives:
Potentially significant erosion.

 

All Alternatives:
No impact.

All Alternatives:
Potentially significant beach erosion.

 

All Alternatives:
Potentially significant beach erosion.

 

All Alternatives:
Potentially significant beach erosion.

 

Alternatives 1,2:
Long-term
benefit of establishment
of beaches.

Alternative 3:
Short-term
benefit to beach
restoration, no
long-term benefit.

 

GEO-4: Increased demand for sediment disposal and potential spread of invasive cordgrass via sediment
disposal.

All Alternatives:
No impact.

All Alternatives:
Potentially
significant impacts related to disposal of dredged
sediments and inadvertent
dispersal of
invasive cordgrass via disposed
sediments.

All Alternatives:
No impact.

All Alternatives:
No impact.

All Alternatives:
No impact.

All Alternatives:
No impact.

All Alternatives:
No impact.

GEO-5: Increased volume and velocity of tidal currents in channels
due to the remoal of invasive cordgrass.

All Alternatives:
Minor impact from localized clearing.

 

All Alternatives:
Potential increase in erosion from increased tidal velocities/currents.

 

All Alternatives:
No impact.

All Alternatives:
Potential increase in erosion from increased tidal velocities/currents.

 

All Alternatives:  Potential increase in erosion from increased tidal velocities/ currents.

 

All Alternatives:
Potential increase in erosion from increased tidal velocities/currents.

 

All Alternatives:
Beneficial effect on tidal channel and creek flows.

 

GEO-6: Increased depth and turbulence of tidewaters impounded in salt marsh pans.

 

All Alternatives:
No adverse
impacts.

.

All Alternatives:
No adverse
impacts.

 

All Alternatives:
No adverse
impacts.

 

All Alternatives:
No adverse
impacts.

All Alternatives:
No adverse
impacts.

 

All Alternatives:
No adverse
impacts.

Alternatives 1, 2:
Permanent
beneficial effect.

Alternative 3:
Temporary
beneficial effect.